ByRuth WalkerOctober 27, 2016

Musician Tom Waits addresses an audience after he and his wife musician Kathleen Brennan were presented with the PEN New England's Song Lyrics of Literary Excellence Award during ceremonies at the John F. Kennedy Library and Museum on Sept. 19, 2016, in Boston.

You know how this goes, dear reader: You hear or read a distinctive turn of phrase, apparently for the first time, and then it pops up again two or three more times in just a couple of days. So it was the other day for me with “You can’t unring a bell.”

It first came up in an NPR story on the US Supreme Court hearing a case involving racially tainted testimony. A lawyer described the problem of trying to get jurors to put impermissible evidence out of their minds, as if they’d never heard it: It’s “impossible to un-ring the bell,” she said.

The Tom Waits song “You Can’t Unring a Bell” includes a line that alludes to the courtroom background of the idiom: “You’ll need an attorney for this journey, Junior.” But the line has moved well beyond the courthouse and is used to mean broadly, “What’s done can’t be undone.”

It does seem, though, a particularly satisfying way to encapsulate the specific problem of tainted testimony. An early example comes from an opinion in a 1912 case before the Oregon Supreme Court: “It is not an easy task to unring a bell, nor to remove from the mind an impression once firmly imprinted there....”

As one contributor to the website The Phrase Finder carefully put it, “Whatever the age and whoever the author, it is an inspired and memorable metaphor, and not yet, I think, actually a cliché.”

Part of what makes the bell metaphor so apt is that it captures the way sound waves move through the air to our ears, leaving no evident physical change – unlike, say, an ocean wave that breaches a sea wall – but rather creating a perception.

A peaceful village looks the same just before the church bell tolls the hour as just after. But once you’ve heard the bells, you know it’s 10 o’clock – or whatever hour.

A more pungent variation on the idea is often quoted in connection with tainted testimony: “If you throw a skunk into the jury box, you can’t instruct the jury not to smell it.” (One legal blog quoting this venerable principle of jurisprudence actually includes a link to a sheet of tips for removing skunk odor.)

Ah, but you can unring a bell.

A biomedical engineering student at the University of Wisconsin-Madison came up a winner some weeks back in GE’s “Unimpossible Missions” innovation challenge. This contest invited science, technology, engineering, and math students to come up with a common idiom of “impossibility” and then demonstrate how the task could indeed be accomplished.

Christopher Nguyen chose “You can’t unring a bell.” As Business Insider explained, he “placed [a] bell on one side of an anechoic chamber – essentially a foam-padded room that traps any sound – and placed a microphone at the other end. In between them was a speaker, which Nguyen pointed at the bell. Whatever sound the bell produces, the speaker is programmed to emit the acoustic opposite.

“When the system works properly, the microphone picks up nothing. The bell gets unrung.”